Theme:
Power plant C&I (IPC) systems
&
Tending to Zero Forced Outage
by
Internalization of Best Practices
Presentation Outline:
1.Some definitions & basics of Pressure, Flow & Temp.
measurement
2. Categorization of C&I systems based on location of application
3. Division of power plant C&I systems based on functionality &
type of application
4.Evolution of C&I systems and latest trend in technology
5.NTPC at a glance and maintenance practices of C&I systems
6. Some case studies
Measurement: Pressure
Outline:

Some Definitions

Pressure Units

Manometers

Elastic Pressure Sensors

Electrical Pressure Sensors

Pressure Switches

Snubbers & Siphon Tubes
Measurement: Pressure
Terminology

Accuracy : Closeness with which an instrument reading
approaches the true value of the variable being measured.

Precision : A measure of reproducibility of the measurements; i.e.
given a fixed value of a variable, precision is a measure of the
degree which successive measurements differ from one another.

Sensitivity : The ratio of output signal or response of the
instrument to a change of input or measured variable.

Resolution : The smallest change in measured value to which the
instrument will respond.

Error : Deviation from the true value of the measured variable.
Measurement: Pressure
Repeatability refers to the ability of a pressure sensor to provide
the same output with successive applications of the same
pressure.
Hysteresis is a sensor's ability to give the same output at a given
pressure while increasing and decreasing the pressure.
Measurement: Pressure
Pressure : Definitions

Definition: Force per unit area

Absolute pressure

Atmospheric pressure

Differential pressure

Gauge pressure
Importance : Pressure measurement is critical for safe and optimum
operation of processes such as steam generation, hydraulic equipment
operation, air compression, vacuum processing etc.
Measurement: Pressure
Zero Reference , Gauge, Absolute, Atmospheric
Pressure

Any pressure above atmosphere is called gauge pressure
 Any pressure below atmosphere is a vacuum (negative gauge pressure)
 Absolute pressure (psia) is measured from a perfect vacuum
Differential Pressure has no reference to either absolute vacuum or atmospheric
pressure
Measurement: Pressure
Units

The SI unit for pressure is the Pascal (Pa);1Pa= 1 N·m-2
Non-SI unit pound (Lb) per square inch (psi) and bar are commonly
used
 Pressure is sometimes expressed in grams-force/cm2or as kgf/cm2
(KSC)
1 atm=1.03 ksc=14.696 psi=760mmHg=10000 mmWC
=101325 Pa
Standard pressure:Pressure of normal (standard) atmosphere is
defined as standard pressure

Measurement: Pressure
Pressure Measuring devices
Manometers
 using water ,mercury and other liquids of known density
 For measuring low pressures.
 Mechanical/Elastic Pressure Sensors
 Electrical Pressure Transducers
 For measuring pressure of all ranges for telemetering purposes.

Manometer:
A
simple pressure standard
May
be used for gauge, differential, and absolute measurements with a suitable
reference.
Useful
mainly for lower pressure work because the height of the column of mercury
will otherwise become very high.
The
difference in column heights gives the pressure reading
Measurement: Pressure
Elastic Pressure Sensors
The basic pressure sensing elements:
A: C-shaped Bourdon tube , B: Helical Bourdon tube , C: flat diaphragm
D: Convoluted diaphragm, E: Capsule , F: Set of bellows
Measurement: Pressure
Electrical Pressure Sensors
1.
2.
3.
4.
5.
Potentiometer Sensor
Inductive
Capacitive
Piezoelectric
Strain Gauge
Usually generate output signals in the mV range (spans of 100 mV
to 250 mV).
 In transmitters, these are amplified to the voltage level (1to 5 V)
and converted to current loops, usually 4-20 mA dc
Measurement: Pressure
Pressure Switches
Applications
• Alarm (Status)
• Shutdown (Hi/Lo Limits)
• Control (ON/OFF)
A “switch” is an instrument that automatically senses some process
variable (such as pressure) and provides an on/off signal relative to
some reference point.
Set Point
Sensing
Element
Conditioning
Circuit
Bourdon Tube
Bellows
Diaphragm
Strain Gauge
Mechanical Switch
Transistor
Measurement: Pressure
High Pressure In High Temperature
* When high process temperatures are present, various
methods of isolating the pressure instrument from the process
are used.
* These include siphons, chemical seals with capillary tubing for
remote mounting, and purging.

Snubbers & its use
 Chemical Seal
 Siphon
Measurement: Pressure
Pressure Snubbers

To filter out pressure spikes, or to average out pressure pulses,
snubbers are installed between the process and the instrument
 Instrument indicates avg pr.
Snubber
Before use
After use
when one is interested in the measurement of fast, transient
pressures (such as to initiate safety interlocks on rising pressures),
snubbers must not be used, as they delay the response of the safety
system.
Measurement: Pressure
Chemical Seal or diaphragm Protector
Chemical seals are used when media can falsify the
pressure measurements due to high temperature, high
viscosity or their property to crystallise
Measurement: Pressure
Siphon
A siphon is a coiled tube. This coil provides a large cooling surface and
the trap created prevents the condensate from draining away.
A siphon is required for hot condensing. fluids, such as steam, to assure
a liquid trap.
It is used to prevent live steam from entering and damaging the device.
It is used to protect the instrument from hydraulic or thermal shocks.
The two most common forms of siphon tube are the 'U' and Pigtail types.
Measurement: Flow
Types of flow meters:
1.
2.
3.
4.
5.
Orifice Flow meter
Vortex flow meter
Ultrasonics flow meter
Coriolis Mass Flow meter
Major issues for selecting flow meters
Orifice Flow-meters
Several sensors rely on the pressure drop
or head occurring as a fluid flows by a
resistance. The relationship between flow
rate and pressure difference is determined
by the Bernoulli equation.
Measurement: Flow
Orifice Flow-meters
• An orifice plate is a restriction with an opening smaller than the pipe
diameter which is inserted in the pipe; the typical orifice plate has a
concentric, sharp edged opening.
•
Because of the smaller area the fluid velocity increases, causing a
corresponding decrease in pressure.
•
The flow rate can be calculated from the measured pressure drop
across the orifice plate, P1-P3.
•
The orifice plate is the most commonly used flow sensor, but it
creates a rather large non-recoverable pressure due to the turbulence
around the plate, leading to high energy consumption.
Measurement: Flow
Venturi Tube
The change in cross-sectional area in the venturi tube causes a
pressure change between the convergent section and the throat,
and the flow rate can be determined from this pressure
drop. Although more expensive that an orifice plate; the venturi
tube introduces substantially lower non-recoverable pressure
drops
Measurement: Flow
Pitot Tubes
Pitot tubes were invented by Henri Pitot in 1732 to measure the
flowing velocity of fluids. Basically a differential pressure (dp) flow
meter, a pitot tube measures two pressures: the static and the
total impact pressure.

Pitot tubes are used to measure air flow in pipes, ducts, stacks,
and liquid flow in pipes, open channels.

While accuracy and rangeability are relatively low, pitot tubes are
simple, reliable, inexpensive, and suited for a variety of
environmental conditions, including extremely high temperatures
and a wide range of pressures.
Measurement: Flow
Pitot Tubes

A single-port pitot tube can measure the flow velocity at only a single point
in the cross-section of a flowing stream.
 The probe must be inserted to a point in the flowing stream where the flow
velocity is the average of the velocities across the cross-section, and its
impact port must face directly into the fluid flow.
Measurement: Flow
Pitot Tubes
The point velocity of approach (VP) can be calculated by taking the
square root of the difference between the total impact pressure (PT) and
the static pressure (P) and multiplying that by the C/D ratio, where C is a
dimensional constant and D is density:

The pitot tube measures the static and dynamic (or impact) pressures of
the fluid at one point in the pipe.

The flow rate can be determined from the difference between the static and
dynamic pressures which is the velocity head of the fluid flow.
Measurement: Flow
Vortex Flow-meters

This measuring principle is based on the fact that vortices are
formed downstream of an obstacle in a fluid flow, e.g. behind a
bridge pillar.

This phenomenon is commonly known as the Kármán vortex
street.
Measurement: Flow
Vortex Flow-meters
This is detected by a sensor, such as capacitive sensor and
fed to the electronic processor as a primary, digitized, linear
signal.
Capacitive
sensors
with
integrated
temperature
measurement can directly register the mass flow of saturated
steam as well.





Universally suitable for measuring liquids, gases and steam
Largely unaffected by changes in pressure, temperature and
viscosity
High long-term stability (lifetime K factor), no zero-point drift
No moving parts
Marginal pressure loss
Measurement: Flow
Ultrasonic flow-meters
Swimming against the flow requires more power and more time
than swimming with the flow. Ultrasonic flow measurement is
based on this elementary transit time difference effect.

Two sensors mounted on the pipe simultaneously send and receive
ultrasonic pulses.
 At zero flow, both sensors receive the transmitted ultrasonic wave at the
same time, i.e. without transit time delay.
 When the fluid is in motion, the waves of ultrasonic sound do not reach
the two sensors at the same time.
Measurement: Flow
Ultrasonic flow-meters

This measured "transit time difference" is directly proportional to
the flow velocity and therefore to flow volume.

By using the absolute transit times both the averaged fluid velocity and
the speed of sound can be calculated.

Ultrasonic flow meters measure the difference of the propagation time
(transit time) of ultrasonic pulses propagating in (normally an inclination
angle around 30 to 45° is used) flow direction and against the flow
direction.

This time difference is a measure for the averaged velocity of the fluid
along the path of the ultrasonic beam
Measurement: Flow
Ultrasonic flow-meters
Advantages:

With homogeneous fluids, the principle is independent of
pressure, temperature, conductivity and viscosity

Usable for a wide range of nominal diameters Direct meter
installation on existing pipes

Non-invasive measurement

No pipe constrictions, no pressure losses

No moving parts. Minimum outlay for maintenance and upkeep
Measurement: Flow
Coriolis Mass Flow-meters


If a moving mass is subjected to an oscillation perpendicular to
its direction of movement, Coriolis forces occur depending on
the mass flow.
A Coriolis mass flow meter has oscillation measuring tubes to
precisely achieve this effect.
Coriolis forces are generated when a fluid (= mass) flows
through these oscillating tubes. Sensors at the inlet and outlet
ends register the resultant phase shift in the tube's oscillation
geometry.
Measurement: Flow
Coriolis Mass Flow-meters
The processor analyzes this information and uses it to
compute the rate of mass flow.
Advantage
This principle is used in a huge range of industry sectors,
including pharmaceuticals, chemicals and petrochemicals, oil
and gas, food etc.
Measurement: Flow
Major issues for selecting flow-meters
Accuracy
Repeatability
Linearity
Reliability
Range/Span
Dynamics(Response time)
Safety
Maintenance
Cost
Measurement: Temp.
Measurement Devices



Thermocouples
Resistance Thermometers
Thermistors

Bimetallic Thermometers

Acoustic Pyrometers

Local Instruments
Measurement: Temp.
Thermocouple
IT IS BASED ON ‘SEEBECK’ EFFECT WHICH SAYS THAT
WHEN HEAT IS APPLIED TO A JUNCTION OF TWO
DISSIMILAR METALS AN ‘EMF’ IS GENERATED WHICH
CAN BE MEASURED AT THE OTHER JUNCTION
T/C Connection
COMPENSATING CABLE
HOT JUNCTION
TO DDC CARDS
TERMINAL END
CJC BOX
Measurement: Temp.
Thermocouple
Types of T/C:E,J,K,T,R,S,B
K (Chromel & Alumel; Ni-Cr &Ni-Al) Type: mostly used in power plant for
low temp. application )
R (Platinum & Platinum-Rhodium) Type: Used for high temp. application.
Highly resistant to oxidation & corrosion
Advantages: Disadvantages: - Low Cost
- Sensitivity low & low voltage output
- No moving parts, less likely to be broken.
susceptible to noise
-Wide temperature range.
- Accuracy not better than 0.5 °C
-Reasonably short response time.
- Requires a known temperature
- Reasonable repeatability and accuracy.
reference
Measurement: Temp.
RESISTANCE THERMOMETER (RTD)
THE RESISTANCE OF A CONDUCTOR CHANGES WHEN ITS
TEMPERATURE IS CHANGED .THIS PROPERTY IS UTILISED TO
MEASURE THE TEMPERATURE.
Rt = Ro (1+βdT)
β = TEMP CO- EFFICIENT OF RESISTANCE ; dT = TEMPERATURE DIFFERENCE
When discussing RTDs, following must be considered:
WHERE
•
•
•
•
•
•
Wiring configuration (2, 3 or 4-wire)
Self-heating
Accuracy
RTD types:
Stability
1. Platinum (Range -200 °C to 600 °C )
Repeatability
2. Copper (Range -100 °C to 100 °C )
Response time
3. Nickel (Range -60 °C to 180 °C )
Measurement: Temp.
THERMISTORS
THERMISTORS ARE GENERALLY COMPOSED OF SEMICONDUCTOR
MATERIALS.THEY HAVE A NEGATIVE COEFFICIENT OF TEMPERATURE SO
RESISTANCE DECREASES WITH INCREASE IN TEMP.
Making use of Negative Temperature Coefficient characteristics,
thermistor and can be applied in temperature compensation, inrush
current limit, precision temp. control (temp. coefficient very large
compared to RTC & T/C) etc.
BIMETALLIC THERMOMETERS


ALL METALS EXPAND OR CONTRACT WITH TEMPERATURE
THE TEMPERATURE COEFFICIENT OF EXPANSION IS NOT THE SAME FOR
ALL METALS AND SO THEIR RATES OF EXPANSION AND CONTRACTION
ARE DIFFERENT
USAGE: IN PROCESS INDUSTRIES FOR LOCAL TEMPERATURE MEASUREMENTS
OVERLOAD CUTOUT SWITCH IN ELECTRICAL APPARATUS
Measurement: Temp.
ACOUSTIC PYROMETER

Acoustic Pyrometer is a non-contact measurement device that
obtains highly accurate instantaneous gas temperature data in any
area of the boiler, helping improve combustion efficiency.

For measurement of temperatures across large spaces of known
distance in a noisy, dirty and corrosive environment such as a coalfired utility boiler, or a chemical recovery boiler.

The Velocity of Sound in a medium is proportional to the Temperature.
LOCAL INDICATION

LIQUID IN GLASS THERMOMETER

MERCURY IN STEEL THERMOMETER

BIMETALLIC THERMOMETER
Power Plant C&I systems
1.Field instruments/ input & output instruments
a)
Various measuring instruments like Transmitters, RTD,
Thermocouples, Pr. & temp. gauges, speed & vibration
pick ups etc. (Analog inputs)
b)
Various Pr., Temp. & limit switches, for Interlock ,
protections & feedback of control element (Binary
inputs)
c)
Output devices like solenoids, EP converters,
Positioners etc. for controlling final control element
d)
Final control elements like Power cylinder, Pneumatic/
motorized actuators etc.
Power Plant C&I systems
2. Control Systems
a)
Various control cabinets for acquiring field signal (both
analog & binary inputs), processing the signals as per control
logic and issuing output command to output devices (Binary
& analog).
b)
Various control desk devices like command consoles, Push
button modules, indicators, recorders, CRTs, PC based
Operator Work Stations (OWS) etc. for human machine
interface for monitoring & control of the plant
c)
Power supply system(UPS)/ chargers with battery backups to
ensure uninterrupted power supply of desired quality for the
control system
Power Plant C&I systems
3. Analyzers
The availability, reliability & efficiency of boiler unit hinge around
the close control of chemical regimes of working fluid i.e. water/steam
as well as combustion in the boiler. The instruments monitoring the
chemical regimes and combustion are generally called analytical
instruments. These instruments fall under three category
i)
Water/ Steam Analyzers
ii)
Gas analyzers
iii)
Smoke monitors
HIGH PURITY WATER IS ESSENTIAL TO MINIMISE

SCALING

CORROSION

CARRY OVER

EMBRITTLEMENT
Power Plant C&I systems
ANALYZERS AND MEASURMENT LOCATION
a)
ON LINE gas analyzers for measurement of flue gas oxygen,
carbon mono-oxides, carbon di-oxides, oxides of sulpher & nitrogen
at various location of boiler.
b)
ON LINE analyzers for measurement of conductivity, pH, silica,
dissolved oxygen, phosphate, hydrazine, chloride, sodium etc. at
various points in the water & steam cycle of boiler & turbine area
(SWAS-steam & water analysis system).
c)
ON-LINE opacity monitors for measurement of dust concentration in
flue gas
d)
ON LINE analyzers for measurement of conductivity, pH, silica,
dissolved oxygen etc. at various ION exchangers of DM plant .
Power Plant C&I systems
TYPICAL VALUES OF CHEMICAL PARAMETERS BEING MEASURED (SWAS)
SAMPLE
PARAMETER
DM WATER
a) Conductivity
b) Cation Conductivity
Condensate
pump
discharge
(CEP)
a) Conductivity
b) Cation Conductivity
Economizer
Inlet
Boiler water
a) Conductivity
b) Cation Conductivity
UNIT
µS/cm
µS/cm
c) pH
<5
<0.3
9.0-9.2
d) Na+
ppb
<5ppb
e) Dissolve oxygen (DO)
ppb
<10
c) Hydrazine
a) Conductivity
µS/cm
ppb
<5
<0.3
µS/cm
100
10-20
9.1-9.4
b) pH
Sat & Main steam
LIMIT
<0.3
c) Silica
ppb
100
a) Conductivity
b) Cation Conductivity
µS/cm
<5
<0.3
Power Plant C&I systems
4. Laboratory Instruments & Setup
Activities of C&I Lab

CALIBRATION

REPAIR

TESTING
with proper documentation & records
CALIBRATION:
 Pressure switch , Transmitter , Gauge

Temperature switch , Transmitter , Gauge

Flow Transmitter

Level Switch
Power Plant C&I systems
4. Laboratory Instruments & Setup
REPAIR:
1. ELECTRONIC CARDS
3. POWER SUPPLY MODULES
TESTING:
1. ELECTRONIC MODULES
2. RELAYS
3. POWER SUPPLY MODULES
Power Plant C&I systems
4. Laboratory Instruments & Setup
a)
Different standard instruments with traceability up to national
standard . These insts. include Standard Gauges, Multimeters,
Resistance boxes, mA sources, oscilloscope, signal generator etc.
for calibration of measuring instruments.
b)
Dead Weight tester, Comparator, Temperature bath, Vacuum
pump, manometer, soldering stations etc.
c)
Test benches with standard power supply sockets (e.g. 24VDC,
48VDC, 220VDC, 110VAC, 230VAC etc.) in each bench depending on
requirement.
d)
Laboratory should be air-conditioned with monitoring of temp.,
humidity and barometric pressure. Also, proper provision for
handling electronic cards (floor mats, ESD protective bags/ anti
static bags etc.)
Power Plant C&I systems
4. Laboratory Instruments & Setup
Essential Tools/ Infrastructure for Repairing & testing
1.
IN-CITCUIT IC TESTER
2.
ESD WORK STATION
3.
ULTRASONIC CARD CLEANER
4.
STORRAGE OSCILLOSCOPE
5.
LOGIC ANALYSER
6.
THERMOCOUPLE SIMULATOR
7.
VIDEO PATTERN GENERATOR
8.
EPROM PROGRAMMER
Power Plant C&I systems
C&I systems of Boiler
-
FSSS (Furnace safeguard supervisory system)
-
Open loop control system (interlock &
protections) of boiler auxiliaries
-
Secondary Air Damper control system (SADC)
-
Hydrastep for drum level measurement
-
Measurements, Protection & Control of Coal
Feeders
Power Plant C&I systems
FSSS
FUNCTIONS OF F.S.S.S
1.
FURNACE PURGE SUPERVISION
2.
OIL GUNS ON/OFF CONTROL
3.
PULVERISERS/FEEDERS ON/OFF
4.
SECONDARY AIR DAMPERS CONTROL
5.
FLAME SCANNER INTELLIGENCE
6.
BOILER TRIP PROTECTIONS
CONTROL
Power Plant C&I systems
FSSS
WHY AT ALL A PROTECTIVE SYSTEM IS REQUIRED FOR THE
BOILER?
THE BOILER’S FURNACE IS CONTINUOUSLY FED WITH HIGH
CALORIFIC VALUE ATOMISED FUEL WHICH IS IN THE PROCESS OF
CONTINUOUS BUT CONTROLLED COMBUSTION.
COMBUSTION-THE PROCESS
COMBUSTION IS A RAPID BURNING OF OXYGEN WITH FUEL RESULTING
IN RELEASE OF HEAT. AIR IS ABOUT 21% OXYGEN AND 78% NITROGEN BY
VOLUME. MOST FUELS CONTAIN CARBON, HYDROGEN AND SULPHUR. A
SIMPLIFIED COMBUSTION PROCESS COULD BE
CARBON+OXYGEN=CARBONDIOXIDE+ HEAT
HYDROGEN+DO =WATER VAPOUR + HEAT
SULPHUR +DO =SULPHURDIOXIDE+ HEAT
WHICH MEANS THAT THE FINAL DESIRED PRODUCT OF THE
PROCESS IS HEAT WHICH WE REQUIRE TO BOIL THE WATER
Power Plant C&I systems
FSSS
COMBUSTION-THE PROBLEM : WHEN THIS CONTROLLED BURNING
GOES OUT OF CONTROL DUE TO AN IMBALANCE IN THE FUEL/AIR
RATIO, THERE IS EITHER A FUEL RICH MIXTURE OR A FUEL LEAN
MIXTURE. IN BOTH CASES THE FLAME QUALITY BECOMES POOR.
THERE IS A CHANCE OF FUEL ACCUMULATION WHICH CAN LATER ON
IGNITE SUDDENLY AND CAUSE EXPLOSIONS.
SO FSSS IS USED FOR SAFE AND ORDERLY STARTUP AND
SHUTDOWN OF BOILER THROUGH VARIOUS INTERLOCKS AND
PROTECTIONS
THE PROTECTIVE SYSTEM IN THE BOILER IS DESIGNED
BASICALLY TO PREVENT OCCURRENCE OF SUCH SITUATIONS BY
TAKING ADVANCE ACTIONS.
Power Plant C&I systems
N.F.P.A Guide line & Boiler Protection

N.F.P.A- National Furnace Protection Association,
USA

Deals with protection for various types of furnace

Protection of Pulverized fuel fired boiler is governed by
Section-85c

Different categories of protection:

a) Mandatory, b)Mandatory & automatically generated, c)
Optional but alarm has to be there
Power Plant C&I systems
BOILER FLAME & FLAME SCANNERS
It looks rather static, but in
reality the fire energy fluctuates
rapidly. The Fuel and Oxygen in
the uncontrolled fire constantly
burn as in small explosions
and then sucks new Fuel &
Oxygen to the flames. This
process causes the flame
flicker.
Flicker frequency for oil
flame is more than that of coal
flame.
Power Plant C&I systems
INTENSITY RELATIVE TO WAVELENGTH
Power Plant C&I systems
FLAME SCANNERS
-UV Scanners
-Visible Range Scanners (Safe scan-1&2)-Used for both Oil & Coal
Flame
-IR Scanners (UR600 of ABB)
SAFE FLAME SCANNER
Power Plant C&I systems
C&I systems of Turbine
-
ATRS (Automatic Turbine Runup system)
Turbine Governing System
-
Turbovisory Instruments & turbine protections
-
Interlock, Protection & Control of HPBP system
-
Open loop control system (interlock & protections) of
turbine auxiliaries
Interlock & protections of Seal Oil & Stator water
system
-
-
Power Plant C&I systems
C&I systems for control & MIS
-Automatic Control System (ACS)
-DATA Acquisition system(DAS)
-Distributed Digital Control Monitoring
and Information System
Power Plant C&I systems
AUTOMATIC CONTROL SYSTEM & POWER PLANT CONTROL LOOP
PROCESS: Process refers to the method of changing or refining raw
materials to create the desired end product. The raw materials may
undergo physical, chemical, or thermal state changes during the
Process.

Process is of Two Types :
A) Continuous and B) Batch
Continuous Process is one where the change of state of Input into
Output occurs continuously.
Ex.: Power Plant Process, Petroleum Industry etc.
Batch Process is one where a Batch of the Product is produced and
the Process stops till production of next Batch is started.
Ex.: Automobile Production
Power Plant C&I systems
AUTOMATIC CONTROL SYSTEM & POWER PLANT CONTROL LOOP
PROCESS CONTROL: Process control techniques are developed
over the years to have
 Quality of the end product
 Economy of production
 Ability to cater to emergencies and bring the process to safe
shutdown.
CONTROLLED CONDITION: The physical quantity or condition of a
process or machine which is to be controlled
CONTROL SYSTEM: An arrangement of elements interconnected and
interacting in such a way that it can maintain some condition of a
process or machine in a prescribed manner
Power Plant C&I systems
AUTOMATIC CONTROL SYSTEM & POWER PLANT CONTROL LOOP
OPEN AND CLOSED LOOP CONTROL:
A Closed Loop Control (CLCS) is one where a
Process Variable is measured, compared to a Set Value and
action is taken to correct any Deviation or Error from Set
Value. The continuous Measurement of PV and its’
comparison to Set Point closes the Loop.
An Open Loop Control(OLCS) is one where the PV is not
compared with Set Value and action taken, but action is
taken without regard to conditions of PV.
Power Plant C&I systems
AUTOMATIC CONTROL SYSTEM & POWER PLANT CONTROL LOOP
OPEN LOOP CONTROL:
Open Loop Control is accomplished by the following means:






Group Control
Sub-Group Control
Sub-Loop Control
Drive Level Control
Programmable Logic Control(PLC)
Group Control : Start and Stoppage of a Group of equipment is
accomplished by Group Control(GC).
Ex. :CEP GC, Equipment Cooling GC etc.
Power Plant C&I systems
AUTOMATIC CONTROL SYSTEM & POWER PLANT CONTROL LOOP
OPEN LOOP CONTROL:
Sub-Group Control : Start and Stoppage of an equipment with its’
associated auxiliaries in Step-Sequence manner is done by SubGroup Control. Operator intervention is not required in Sub-Group
Control(SGC).
Sub-Loop Control: Start and Stoppage of auxiliaries of an
equipment is carried out by Sub-Loop Control(SLC)
Drive Level Control : Start and Stop or Opening and Closure of a
Drive is carried out by Drive Control. The Drive logic shall have
Protection, release ,auto and manual commands and these are
executed as per pre-determined logic.
Power Plant C&I systems
AUTOMATIC CONTROL SYSTEM & POWER PLANT CONTROL LOOP
CLCS TERMINOLOGY:
Desired Value or Set Point : The value of the variable/parameter which
needs to be controlled at the required condition.
Process Variable(PV) : The present value of the Parameter of Process at
that particular instant. This is sometimes referred as Measured Value.
Error/Deviation : It is the Difference between Set Point and Process
Variable, and can be +ve or –ve. It has three components: a) Magnitude b)
Duration and c) Rate of change.
Controller : A Controller is a device that receives data from a
Measurement Instrument, compares the data with the Set Point and if
necessary, signals a Control element to take Corrective action. This
Corrective action ensures that the PV shall always be maintained at the
Set Value.
The Controller can be a) Electronic, b) Pneumatic and c) Hydraulic type.
Power Plant C&I systems
AUTOMATIC CONTROL SYSTEM & POWER PLANT CONTROL LOOP

Controller types: Functionally, Controllers can be
a) Continuous and b) Step Controllers.
Depending on the control loop; controller action can be adjusted
as (i) Direct acting:-Increase of process value increases controller
output
(ii) Reverse acting:- Increase of process value decreases
controller output

Control Element : The Control or Correcting Element is the part of
the Control System that acts to physically change the Manipulated
Variable.
Ex. : Control Valves, Louvers or Dampers, Solenoids, Pump
Motors etc.
Power Plant C&I systems
AUTOMATIC CONTROL SYSTEM & POWER PLANT CONTROL LOOP

Bump less Transfer : The arrangement where the transfer from auto
to manual mode does not affect the process.

Proportional Control : The Proportional (P) action responds only to a
change in the magnitude of Error(e) i.e. controller output changes by
an amount which is proportional to error.
Output change of Controller in % = (Error change in %)(Gain),
where Gain is called the Controller gain. The reciprocal of Gain is
termed as Proportional Band(PB) and is expressed in %.
Proportional Band(PB): The change in deviation required to cause
the output of the controller to change from one extreme to the other.

Integral Control : In Integral Control, the Controller output is a
function of the Duration of Error(e).
Power Plant C&I systems
AUTOMATIC CONTROL SYSTEM & POWER PLANT CONTROL LOOP
Hence, the Controller output is the time Integral of Error and the time
set is Integral Action Time(IAT) i.e. IAT can be defined as time taken for
the integral action to change output by the same amount as the
proportion action .
Usually, both P and I Controls are combined and the Controllers are
tuned to minimize Error(e) and controller is termed as PI controller.
Derivative Control : Derivative or Rate Controller’s output is Proportional
to the rate of change of Error(e). The Control action is termed as D. The
action is to apply an immediate response that is equal to the P+I action
that would have occurred some time in the future.
Power Plant C&I systems
AUTOMATIC CONTROL SYSTEM & POWER PLANT CONTROL LOOP
Important Closed Loop Controls in a Thermal Power Plant:
a) Furnace Draft Control
b) Boiler Drum Level Control
c) HOT well & D/A level control
d) Main Steam Temperature Control
e) Air and Fuel Flow to Boiler Control
f) SH & RH spray control
g) Coordinated Master Control(CMC)
h) Turbine Speed, Pressure and Load Control
Power Plant C&I systems
AUTOMATIC CONTROL SYSTEM & POWER PLANT CONTROL LOOP
Coordinated Master Control
This is an integrated automatic control of unit operation. There is a
continuous co ordination between boiler and turbine control to
maintain a balance between steam generation and steam
consumption.
•
Boiler Follow Mode (BFM)
•
Turbine Follow Mode (TFM)
•
Co-ordinated Master Control (CMC)
•
Runback Mode
Power Plant C&I systems
AUTOMATIC CONTROL SYSTEM & POWER PLANT CONTROL LOOP
Boiler Follow Mode (BFM)
•
Unit load control from turbine local load set point
•
Change in turbine load set point will modulate turbine CVs
•
Boiler master output gets corrected to maintain throttle pr dev.
•
Boiler control will follow turbine control
•
BLI signal as feed forward signal for boiler firing rate control
•
Result - Boiler acts as throttle pr controller where turbine is in load controller
mode
Power Plant C&I systems
AUTOMATIC CONTROL SYSTEM & POWER PLANT CONTROL LOOP
Turbine Follow Mode (TFM)
•
Unit target load set point goes to boiler master
•
Change in BLI will modulate turbine CVs
•
Boiler master output gets corrected to maintain Unit load dev.
•
Turbine control will follow boiler control
•
Load deviation as feed orward signal for boiler firing rate control
•
Result - Boiler acts as load controller where turbine is in pressure controller
mode
Power Plant C&I systems
AUTOMATIC CONTROL SYSTEM & POWER PLANT CONTROL LOOP
Coordinated Master Control
•
Unit load is set from unit master.
•
Unit master demand is limited by unit capability , TSE margins and unit
max/min load set points.
•
Unit target load is derived from unit master after the limitations.
•
Unit target load is used as feed forward signal to the boiler firing rate control.
•
Turbine control utilises the unit load as turbine load set point after adapting
the same by steam generation delay.
•
In TG throttle pressure is maintained by correcting the BMD output depending
on the throttle pr dev.
•
Result: Balance is achieved between steam generation and steam
consumption PROPER COORDINATION BETWEEN BOILER CONTROL AND
TURBINE CONTROL
Power Plant C&I systems
DATA ACQUISITION SYSYTEM-DAS
WHY DAS IS REQUIRED IN THERMAL POWER PLANTS ?

SAFE & RELIABLE OPERATION OF THE UNIT OR EQUIPMENTS

ASSIST CONTROL ROOM OPERATORS BY PROVIDING TIMELY
ANNUNCIATION OF ALL ABNORMAL CONDITIONS

PROVIDE DETAILED INFORMATION ON THE PLANT PERFORMANCE

PROVIDE MANAGEMENT WITH ACCURATE RECORDS ON THE PAST
PLANT PERFORMANCE FOR ANALYSIS
Power Plant C&I systems
DATA ACQUISITION SYSYTEM
3 MAJOR FUNCTIONS OF DAS:

DATA ACQUISITION

DATA PROCESSING

DATA REPRESENTATION
The Major Parts




Process Control Units ( PCU )
Computer Interface Unit ( CIU )
Termination Units ( TU )
Buffer Terminal Cabinets ( BTC )
Power Plant C&I systems
DATA ACQUISITION SYSYTEM
TYPES OF DATA (Input): Analog & Digital




Analog inputs:
1. Thermocouple Input ( mV )
K-Type T/C ( Cr-Al ) : For temp < 600 Deg C& used in Flue
Gas path after FSH outlet.
R-Type T/C ( Pt-Pt-Rh ) : For temp > 600 Deg C used in PSH
& FSH region of FG path.
2. RTD Input ( Resistance )
Pt-100 RTD : For Brg. Temp measurement.
Cu-53 RTD : For HT motor & Generator Stator winding
temp. measurement.
Power Plant C&I systems
DATA ACQUISITION SYSYTEM
Analog inputs:
3. 4 – 20 Ma Input




Coming from Pr. / Flow Transmitters.
Coming from Signal Distribution Cards of automatic
control system
4. 0 – 10 Volt Input
Coming from ATRS cabinets
Used for Turbine Brg. Temp. /Vibration measurement.
DIGITAL INPUTS
These are coming directly from switches or relay contacts
of other systems (FSSS, ATRS, ACS etc.)
Power Plant C&I systems
DATA ACQUISITION SYSYTEM
DIGITAL INPUTS (TYPES)



LOW RESOLUTION : The scanning time of inputs is 1
second.
HIGH RESOLUTION : The scanning time is 1
millisecond. These are called
Sequence Of Events ( SOE )
Inputs.
PULSE INPUT
: For calculation of Total Coal
Flow, Total Air Flow etc.
Power Plant C&I systems
DATA ACQUISITION SYSYTEM
FUNCTIONS OF DAS:
 Alarm Management.
 Production of hardcopy print outs in different
printers.
 Operator Guidance Messages.
 Graphic Displays of plant sub-systems.
 Trending of analog variables on recorders.
 Sequence Of Events ( SOE ) recording following
unit / equipment trip conditions.
 Efficiency calculations
Power Plant C&I systems
DATA ACQUISITION SYSYTEM
DATA PROCESSING: It has the following parts

COMPUTER PROCESSING UNIT ( CPU )

BULK ( SOLID STATE ) MEMORY WITH BATTERY BACKUP

MAGTAPE UNIT

COMMUNICATION CABINET & MODEM

MOVING HEAD DISC DRIVE

VIDEO HARD COPIER

TREND RECORDER

UNIT CONTROL DESK & PROG. ROOM CRT

PRINTERS
Power Plant C&I systems
Features:


DATA ACQUISITION SYSYTEM
REAL TIME VARIABLE CALCULATION
Summing, Subtraction, Maximum , Minimum, Averaging,
Hourly & Daily integration, rate of changes & comparison of
limits etc.
ON-LINE DATABASE EDITION
1. Assign points to any process parameter
2. Scan, Off-scan , Delete , Activate , inactivate a process
parameters , calculated points when reqd.
3. Change the Engg. Unit
4. Change the range , alarm limits & dead bands
5. Change the scan frequency
6. Review total analog and digital points depending on its
quality flag like alarm , channel failure , off-scan etc.
Power Plant C&I systems
DATA ACQUISITION SYSYTEM
ALARM MANAGEMENT:
 All the analog points which cross their normal limits or all the
digital points which go into their alarm state come on the alarm
CRT with associated time & blink as long as the alarms remain
unacknowledged.

Alarm will come in RED colour

If all the pages are full (normally no. of alarm pages & alarm per
page is predefined) and any new alarm comes , then oldest alarm
will disappear from the alarm page as FIFO basis

Alarm print out will be available in alarm printer
Power Plant C&I systems
DATA ACQUISITION SYSYTEM
DATA REPRESENTATION:

Printed outputs of displays /collection of data in
different formats like :
1.
Copy Screen
2
Alarm Print out
3.
Log Print out

CRT Displays
1.
Alarm CRT display
2.
Utility CRT display
Power Plant C&I systems
DATA ACQUISITION SYSYTEM
DATA REPRESENTATION:
TYPES OF TREND LOG

TIME ACTIVATED

EVENT ACTIVATED

DEMAND LOGS

SOE PRINTOUT
TIME ACTIVATED LOG:

Automatic Triggered Logs
 Sample frequency is 1 Hour.(Normally)
 Time of trigger can be specified
PRINOUTS
Power Plant C&I systems
DATA ACQUISITION SYSYTEM
TIME ACTIVATED LOG:
Max. 15 nos. of points can be assigned
 Normally printed in the logging printer in UCB
 Examples :
1.
Shift Log
2.
Efficiency Log
3.
Boiler Drum / Tube Metal Temp. Log
4.
FSH / RH Metal temp. excursion Log

EVENT ACTIVATED LOG:

Automatic Triggered Logs

Used for Unit or Equipment Outage Analysis

Minimum Sample frequency is 10 seconds.
Power Plant C&I systems
DATA ACQUISITION SYSYTEM
EVENT ACTIVATED LOG:
 Max. 36 points can be assigned in a log

Logs are triggered by a Trip flag
 Normally printed on Logging Printer in UCB
 Pre & Post triggered points can be specified
 Examples :
1. Post Trip Analysis Log ( PTL )
2. TG. Shutdown Analysis Log
3. Boiler Startup Log.
4. Turbine / Generator Diagnostic Logs
Power Plant C&I systems
DATA ACQUISITION SYSYTEM
DEMAND LOG:

Not Automatic Triggered Logs

Logs can be printed on operator’s demand

Sample frequency is generally 1 Hour.

Logs are printed in Logging Printer in UCB
Power Plant C&I systems
DATA ACQUISITION SYSYTEM
SEQUENCE OF EVENTS ( SOE )
THE MAIN FEATURES ARE:

Determines First Cause Of Trip

Determines sequence of events or alarms

Scanning Time is 1 millisecond.

It is a Stand Alone System

Max. 256 nos. of Protection related digital points can be
assigned

Automatic Triggered when any point in alarm
Power Plant C&I systems
DDCMIS
WHAT IS DDCMIS ?
DISTRIBUTED DIGITAL CONTROL MONITORING &
INFORMATION SYSTEM

Distributed means there is no centralized control and control is spread
across multiple units

Digital means processing of process information is done in digital form
using micro-processor based hardware

MIS interfaces the human with process using computers
Power Plant C&I systems
DDCMIS
TECHNOLOGICAL BACKGROUND
PROGRESS OF INSTRUMENTATION USED TO IMPLEMENT AUTOMATIC
PROCESS CONTROL

LOCAL PNEUMATIC CONTROLLERS

MINIATURIZED AND CENTRALIZED PNEUMATIC CONTROLLERS
AT CONTROL PANELS AND CONSOLES

SOLID-STATE CONTROLLERS

COMPUTERISED CONTROLS

DISTRIBUTED MICROPROCESSOR BASED CONTROL
Power Plant C&I systems
DDCMIS
Components
MAN MACHINE INTERFACE & PROCESS
INFORMATION SYSTEM
DATA COMMUNICATION SYSTEM (DATA HIGH WAY)
CONTROL SYSTEM
Power Plant C&I systems
DDCMIS
MAN-MACHINE INTERFACE AND PLANT INFORMATION SYSTEM (MMIPS)

LATEST STATE-OF-THE-ART WORKSTATIONS AND SERVERS BASED ON
OPEN-ARCHITECTURE AND INDUSTRY STANDARD HARDWARE AND
SOFTWARE TO ENSURE BETTER CONNECTIVITY.
e.g. HARDWARE FROM COMPAQ/DIGITAL, HP, SUN MICRO-SYSTEM OR
OTHER MAJOR SUPPLIERS (LESS DEPENDENCE ON THE C&I SYSTEM
SUPPLIER IN THE LONG RUN)

OPERATING SYSTEM WINDOWS-NT, OPEN-VMS OR UNIX.

PROVISION OF LVS

CONNECTION TO OTHER SYSTEM THROUGH STATIONWIDE WAN
Power Plant C&I systems
DDCMIS
MMIPIS FUNCTIONALITIES

VARIOUS PLANT EQUIPMENT OPERATION

OPERATOR INFORMATIONS THROUGH VARIOUS DISPLAYS

ALARMS, LOGS, HISTORICAL AND LONG TERM STORAGE.

PERFORMANCE AND OTHER CALCULATIONS
Power Plant C&I systems
DDCMIS
DATA COMMUNICATION SYSTEM

LOCAL SYSTEM BUS – It is just lines on the backplane of control
panel to which all the modules are connected directly. It serves as
communication medium between the modules.

INTRAPLANT BUS(IPB) – It is a coaxial cable which runs through
all the panels of control system and interconnects them.

LOCAL AREA NETWORK(LAN) – It is a network of computers
which are connected to a single point (HUB).
FOR ALL BUSES REDUNDANCY IS PRESENT
Power Plant C&I systems
DDCMIS
CONTROL SYSTEM
FUNCTIONAL DIVISION
 SG-C&I SYSTEM
 TG-C&I SYSTEM
 BOP-C&I SYSTEM
HARDWARE COMPONENTS
 POWER SUPPLY
 CONTROL PANEL
 ELECTRONIC MODULES
Power Plant C&I systems
DDCMIS
CONTROL SYSTEM
PROGRAMMING &
CONFIGURATION
MMIPIS
SYSTEM
M&S
CLOCK
DCS
SG- C&I
SYSTEM
BOP- C&I
SYSTEM
TG- C&I
SYSTEM
Power Plant C&I systems
DDCMIS
SG-C&I SYSTEM

BURNER MANAGEMENT SYSTEM (BMS)

SOOT BLOWER CONTROL SYSTEM (SBC)

SECONDARY AIR DAMPER CONTROL SYSTEM (SADC)

AUXILIARY PRDS CONTROLS (APRDS)
TG-C&I SYSTEM

ELECTRONIC TURBINE PROTECTION (ETP)

AUTOMATIC TURBINE RUN-UP SYSTEM (ATRS)

AUTOMATIC TURBINE TESTING SYSTEM (ATT)

ELECTRO- HYDRAULIC TURBINE CONTROL SYSTEM (EHTC)

TURBINE STRESS CONTROL SYSTEM (TSC)

LP BYPASS SYSTEM (LPBP)

HP BYPASS SYSTEM(HPBP)

GLAND STEAM PRESSURE CONTROL

GENERATOR AUXILIARY MONITORING PANEL (GAMP)
Power Plant C&I systems
DDCMIS
BOP-C&I SYSTEM
CONSISTS OF OPEN LOOP CONTROL SYSTEM (OLCS) AND CLOSED
LOOP CONTROL SYSTEM (CLCS)

OLCS - THE SEQUENCE CONTROL, INTERLOCK OF ALL THE PLANT SYSTEMS
WHICH ARE NOT COVERED IN THE SG-C&I AND TG-C&I. THIS INCLUDES MAJOR
AUXILIARIES LIKE FD/ID/PA FANS, AIR-PREHEATER, BFP/CEP/CWP/ BCWP ,
DMCWP/CLCWP AND ELECTRICAL BREAKERS.

CLCS
- THE MODULATING CONTROL FOR VARIOUS IMPORTANT PLANT
PARAMETERS, LIKE FW FLOW (DRUM LEVEL), FURNACE DRAFT, COMBUSTION
CONTROL (FUEL FLOW AND AIR FLOW), PA HDR PRESSURE CONTROL,
DEAERATOR/HOTWELL/HEATER LEVEL CONTROLS ETC.
Power Plant C&I systems
DDCMIS
WHY DDCMIS ?

VERY HIGH FLEXIBILITY FOR MODIFICATION

VERY HIGH SELF-DIAGNOSTIC
IN CONTROL STRATEGY

VERY LOW DRIFT (ONLY IN I/O CARDS) , HENCE
FREQUENT RE-CALIBRATION

MUCH HIGHER RELIABILITY (BASED ON MTBF)

BETTER LONG TERM SUPPORT DUE TO

MUCH BETTER OPERATOR INTERFACE
NO NEED OF
CHANGING TECHNOLOGY
Power Plant C&I systems
DDCMIS
SALIENT FEATURES OF DDCMIS

INTEGRATED PLANT CONTROL FOR SG, TG AND BALANCE OF
PLANT CONTROL
IT MAY BE REMEMBERED THAT HISTORICALLY THE TERM DDCMIS
USED REFER TO THE SO-CALLED “BOP-C&I” . THE SG-C&I, i.e. FSSS etc.
TG-C&I i.e. ATRS, TURBINE PROTECTION etc. ORIGINALLY WERE NOT
CONSIDERED UNDER DDCMIS OR DCS AS PER MANY SUPPLIERS. ONLY
RECENTLY THE TYPE OF SYSTEMS FOR ALL THE SYSTEMS HAVE
BECOME SIMILAR (WITH SOME DIFFERENCE WHICH WILL BE
DISCUSSED LATER), WE TEND TO CONSIDER THESE SYSTEMS UNDER
DDCMIS.
Power Plant C&I systems
DDCMIS
SALIENT FEATURES OF DDCMIS

INTEGRATED PLANT OPERATION THROUGH FULLY INTERCHANGEABLE
OPERTAOR WORK STATIONS (OWS) FOR SG, TG AND BALANCE OF
PLANT

PROVISION OF EXTENSIVE SELF-DIAGNOSTICS

USE OF LARGE VIDEO SCREENS FOR PROJECTIONS OF VARIOUS
PLANT MIMICS ETC.

PROVISION OF FAULT ALARM ANALYSIS TO GUIDE THE OPERATOR TO
THE MOST LIKELY EVENT

PROVISION OF ADEQUATE RELIABILITY AND AVAILABILITY WITH
PROPER REDUNDANCY IN SENSOR, I/O AND CONTROLLER LEVELS.
Power Plant C&I systems
Global & National Power Scenario
Global:
Global electricity consumption 69% higher in 2020 than 2003
80% of energy provided from thermal sources
Emerging trend from Thermal to Hydel and Renewable Energy
sources
Indian:
Total installed capacity only 1362 MW in 1947
Per Capita consumption 631 units (2005-06) only with installed capacity of
1,77,000 MW
GDP growth of 8%, power growth required 10%
To add 1,00,000MW capacity by 2017
Liberalizations of the sector
Power Plant C&I systems
NTPC at a glance:
Installed Capacity 34199 MW
Target 75000MW by 2017
Performance:
Annual Availability 91.62%
Annual PLF 88.29%
11 stations among top 20 in the country
NTPC Practices to achieve goal
KEY THRUST AREAS
Zero Human Error
Implementation of trip committee recommendations judiciously / rigorously
Identification of trip committee recommendations of other stations
which are relevant and implement them
Implementation of operation memorandum wherever applicable
Dissemination of information about best practices followed across
NTPC and other Power Stations
Providing proper environment for C&I equipment to reduce probability of
card and equipment failure
C&I Trip Trend
2009-10: FORCED OUTAGE DISTRIBUTION (COAL)
Coal 09-10
Relay Malfunction
Tx / Sw /Fld Dev
7%
2%
4%
Control System
9%
22%
17%
28%
9%
2%
EHC / ATRS
Power Supply /
Cable
Software / Card
failure
Human Error
UPS
RTD / Tc
INFERENCE : 2009-10 C&I OUTAGE ANALYSIS
Major factors contributing to C&I outage in
2009-10:
1. Control System related failure
2. Field Device Failure
3. Soft ware/Card Failure
4. Power Supply/Relay failure
5. Human error
BEST PRACTICES COMPILED/ADOPTED IN NTPC C&I
All ‘unit protections’ are provided with 2/3 logic and audio visual alarm is
provided on 1/3 to operator on actuation of any one sensor wherever possible
with proper approval.
Use of headless RTD in tripping circuit of ID/PA/FD fans & BFPs.
Resistance mapping of critical solenoids including cable during overhauls and
monitoring trend to identify any defects.
Marking of trip related devices and Junction Boxes marked in RED color.
Regular calibration of all important instruments which have a bearing on unit
safety, reliability and efficiency. Instruments are calibrated against standard
instruments with traceability to NABL.
BEST PRACTICES COMPILED/ADOPTED IN NTPC C&I
For handling of electrostatic sensitive electronic hardware,
electrostatic bags, wrist straps and other ESD handling devices
are employed in control panels and lab. All Laboratories are
provided with ESD proof workstations.
Disable removable drives of servers and workstations.
Single source responsibility for software backup of DCS and
storage in fire proof cabinets in two different locations.
Detailed work instruction are prepared and followed for
working on all trip related devices.
BEST PRACTICES COMPILED/ADOPTED IN NTPC C&I
A single source responsibility is fixed for the generation and
maintenance of system passwords so as to maintain system
security
Internal quality inspection for critical checks during overhauls
to ensure quality in overhaul works
Near miss situations are monitored and analyzed. The
learning from this area used to formulate strategies to avoid
spurious outages.
All power supply voltages are monitored with a fixed
periodicity and maintained within /- 10% of the rated value.
BEST PRACTICES COMPILED/ADOPTED IN NTPC C&I
Fuses used in UPS and protection circuits are replaced with
new fuses of same rating and type during every overhaul
Earth voltages in control panels are monitored on a
predetermined frequency and the values are recorded for
trending
All bus terminators are checked during every overhaul for
ensuring integrity of bus communication in DDCMIS systems
Load testing of power supplies for critical applications and
replacement of power supply modules or electrolytic capacitor
and power transistors used in power supply if found
deteriorated.
Other important actions taken for forced outage reduction
Rerouting of control & power cables in hot zones
Panel power supply monitoring in regular intervals.
CER/UCB temperature and humidity monitoring online.
Insisting for performance of the A/C system
Checking and tightening power supply cables during overhaul
Ensuring healthiness of cabinet cooling fans.
Other important actions taken for forced outage reduction
Panel cooling fans supply segregation from system supply
with MCB / fuse.
Cleaning of air filters on panels periodically
Servo valve replacement/ servicing in hydraulic drives.
Individual fuse protection in 220VDC MFT for HOTV,
LOTV, HORV, Scanner emergency air damper solenoids
Looking from WBPDCL Santaldih Perspective
KEY THRUST AREAS
1. Commissioning of non commissioned systems
a) Soot blowing Steam Pr. Control valve:
Status- Actuator damaged while commissioning. BHEL has placed PO on
OEM M/s MIL for procurement of damaged parts
b) Commissioning of SWAS analyzers:
Status-Procurement of Reagents for reagent based measurement (i.e. Silica
etc.) is in process.
Suggested to take up with OEM (Forbes Marshall) through BHEL for
commissioning of electrode based measurements (i.e. conductivity etc.)
Looking from WBPDCL Santaldih Perspective
c) Electromatic Relief Valve (ERV):
Status- Solenoid Installed and cabling done
d) APH Rotor stop alarm:
Status- Issue pending with BHEL for longtime. Alternative scheme
through DDCMIS suggested by fixing proximity switch on APH rotor
shaft at support brg. end.
e) APH fire detection alarm:
Status- Issue pending with BHEL for longtime. Alternative scheme by
measuring APH metal temp. using thermocouples in Air & Gas path may
be thought of.
Looking from WBPDCL Santaldih Perspective
f) Commissioning/testing of Back up (Back up of MAX DNA
system work stations)Push Button console for unit control:
Suggested to test the operation of various push buttons at the time of Start
up/ Shutdown of unit jointly with operation.
2. Rectification of long pending problems:
a) Problem of SADC systems
Status: Operation of some of the dampers erratic and needed frequent
adjustment due to unreliable performance of actuator/positioner
Suggested to procure 04 nos. actuator with positioner of reputed
manufacturer for replacement in one elevation on trial basis
Looking from WBPDCL Santaldih Perspective
b) High PA flow to Mills:
In auto PA flow of all mills are about 30% more than characteristic flow.
PA flow curve for sliding set point may be set as per mill design.
Also provision of manual set point may be explored to cater poor coal
quality
3. Setting up of C&I Lab with requisite facilities
4.Enhancing reliability of Field Instruments
a)
Proper glanding/ sealing of field instruments, control valves, routing
& dressing of cables, ensuring cleanliness & closure of all LIEs etc.
Looking from WBPDCL Santaldih Perspective
b)
Replacement of unreliable instruments by quality instruments
c) Marking of protection related JBs to avoid human error
Regular walk down check in various areas to ensure the healthiness of field
instruments.
5. Sealing & Cable dressing in MAX DNA panels during unit Shutdown
6. Disabling various ports for removable drives of MAX DNA work
stations for system reliability
7. Installation of ON Line printers of MAX DNA system for daily LOGs.
Daily LOGs are essential for analysis of different plant parameters by
O&E dept.
Looking from WBPDCL Santaldih Perspective
8. Cleanliness of NETWORK ROOM & EWS room to be ensured.
Monitoring of Temp. & Humidity of CER, UCB , NETWORK & EWS
rooms.
9.Implementation of regular cleaning schedule & preventive mtc. Schedule
for Boiler, Turbine and common systems
10.Prepartion of detail job list for unit overhauling
11. Review of spares status and timely action for procurement for
breakdown(corrective), preventive and overhauling maintenance.